The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ecu sends a signal to the ecm to prohibit fuel delivery and ignition, effectively disabling the engine.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ecu. The ecu matches the key's id code with the vehicle's id code, which was previously registered in the ecu and then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingYaw rate and deceleration sensor
Components
Removal
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Remove front seat assembly lh
For manual seat: ...
Theft deterrent system
Engine immobilizer system
The vehicle’s keys have built-in transponder chips that prevent
the engine from starting if a key has not been previously registered
in the vehicle’s on-board computer.
Never leave the keys inside the vehicle when you leave the vehicle.
This system is designed to ...
Glossary of sae and toyota terms
This glossary lists all sae-j1930 terms and abbreviations
used in this manual in compliance with sae
recommendations, as well as their toyota equivalents.
...